Spunbonded heat seal material

ABSTRACT

Disclosed is a nonwoven web material comprising thermoplastic fibers or filaments and a method of manufacture thereof. The web material has properties desirable for use on machinery having conventional heat sealing stations. Also, disclosed is a nonwoven infusion web material comprising thermoplastic fibers or filaments and a method of manufacture thereof. The infusion web material has properties desirable for use in making infusion packages.

This is a divisional of U.S. application Ser. No. 10/297,573 filed Aug.7, 2003 now U.S. Pat. No. 7,935,646, which is the National Stage ofInternational Application No. PCT/US01/40919 filed Jun. 12, 2001.

FIELD OF THE INVENTION

The present invention relates generally to nonwoven web material. Oneaspect of the invention is more particularly concerned with new andimproved extruded web material suitable for use with packing equipmentusing heat and pressure type sealing processes. Another aspect of theinvention is concerned with an extruded web material useful for infusionapplications.

BACKGROUND OF THE INVENTION

Infusion packages for brewing beverages, such as tea bags and coffeebags, are generally produced by enclosing finely ground beverageprecursor materials within a porous web material. The beverage precursormaterials can include tea, coffee, hot chocolate mix and soup mix. Theinfusion package is either placed in a cup or pot containing boilingwater, or alternatively, the infusion package is placed in an empty cupor pot and subsequently boiling water is added. In either event, the hotwater passes through the web material into the bag to extract thebeverage precursor materials and the extract passes outwardly of the bagto form the brew.

Infusion packages are generally made from cellulose fiber based nonwovenweb materials that are free from perforations or punctures yet possess ahigh degree of porosity. Particularly favored for infusion packages havebeen those wet laid fibrous materials made on inclined wire paper makingmachines using long natural fibers. These web materials are generallysoft, tissue-thin fibrous materials characterized by their lightweightand superior infusion characteristics. The fibers used for theproduction of infusion packages are typically regulated by governingagencies for use as packaging for food products.

While it is desirable for the infusion package to allow extraction ofthe beverage precursor materials, physical release of the finely groundbeverage precursor materials from the sealed infusion package into thecup is undesirable. To prevent movement of finely ground beverageprecursor materials from the sealed infusion package into the brewingcontainer, the porosity and “sifting” characteristics of the nonwovenweb material are carefully controlled. Importantly, the seam maintainingthe beverage precursor materials within the infusion package mustmaintain integrity to prevent opening of the infusion package and thesubsequent undesirable discharge of the finely ground beverage precursormaterials into the brew.

Infusion package seams may be of either the “heat seal” or “non-heatseal” variety. In non-heat seal infusion packages, the edges of the webmaterial are brought together, folded a number of times, and thismultiple fold is crimped to provide a mechanical crimped seam whichseals the infusion package. Typically, the nonwoven web material usedfor non-heat seal infusion packages includes a single layer comprised ofvegetable fibers and does not incorporate fusible polymeric fibers.

Heat sealed infusion packages are typically produced from a wet laid,cellulose based nonwoven material comprising two layers or phases. Oneof the phases, the heat seal phase, typically includes more thantwenty-five percent by dry weight of fusible thermoplastic polymericfibers. The surface of the second phase, and typically the second phaseitself, is substantially free of fusible fibers. The web material isfolded so that the phases containing the fusible fibers are in contact.Typically, the folded web material passes between opposing, movablesurfaces such as dies, jaws or rollers that are heated to apredetermined temperature. Actuation of the surfaces toward each otherprovides the required pressure and heat to the folded web material toflow and fuse the touching fusible fibers and create a heat seal seamjoining the layers of web material

The surface of the second phase functions to prevent buildup of themelted polymeric fibers to the heated surfaces of the dies, jaws orrollers. It is important that the heated surfaces remain substantiallyfree of adherent polymeric fibers to ensure proper function of the heatand pressure type sealing equipment.

It is known to use thermoplastic nonwoven materials formed byspunbonding or meltblowing for specialized sealing applications. Most ofthe specialized sealing equipment for such materials uses ultrasonicbonding of the contacting web materials in place of application of heatand pressure. Typically, use of spunbonded or meltblown web materialswith conventional heat seal equipment leads to undesirable thermoplasticmaterial buildup on the heated surfaces. While ultrasonic bonding avoidsthe material buildup problems associated with the use of conventionalheat and pressure type sealing equipment and thermoplastic spunbondedmaterials, it is less efficient than conventional heat-seal techniques.In the high speed preparation of mass produced articles such as infusionpackages, ultrasonic bonding is slower and less cost effective thanconventional heat-sealing techniques and requires modification ofexisting equipment and processes. Additionally, known spunbonded andmeltblown web materials present problems of limpness, tracking andcutting of the web material when used with conventional packingequipment having heat and pressure type sealing processes. Infusionpackages made using spunbonded or meltblown materials also presentproblems of limpness. Further, to be acceptable for infusion packagingweb materials must have a minimum combination of infusion properties andsuch infusion properties are not always present in spunbonded ormeltblown web materials.

DEFINITIONS

Bicomponent fiber—A fiber that has been formed from at least twopolymers extruded from separate extruders through a single spinnerethole to form a single filament. The polymers are arranged insubstantially constantly positioned distinct zones across thecross-section of the bicomponent fibers and extend continuously alongthe length of the bicomponent fibers. The configuration of such abicomponent fiber may be, for example, a sheath/core arrangement whereinone polymer is surrounded by another or a side by side arrangement.

Biconstituent fiber—A fiber that has been formed from a mixture of twoor more polymers extruded from the same spinneret. Biconstituent fibersdo not have the various polymer components arranged in relativelyconstantly positioned distinct zones across the cross-sectional area ofthe fiber and the various polymers are usually not continuous along theentire length of the fiber, instead usually forming fibrils which startand end at random. Biconstituent fibers are sometimes also referred toas multiconstituent fibers.

Cellulose fiber—A fiber comprised substantially of cellulose. The fibersare typically from natural sources such as woody and non-woody plantsalthough regenerated cellulose fibers are also considered cellulosefibers. Woody plants include, for example, deciduous and coniferoustrees. Non-woody plants include, for example, cotton, flax, espartograss, sisal, abaca, milkweed, straw, jute, hemp, and bagasse.

Cross machine direction (CD)—The direction perpendicular to the machinedirection.

Denier—A unit used to indicate the fineness of a filament. The unitexpresses the mass of a filament divided by its length, with a filamentof 1 denier having a mass of 1 gram for 9000 meters of length.

Extruded web material—A sheet material formed by extrusion of at leastone thermoplastic polymer onto a surface to form at least one nonwovenweb. The extruded web material can comprise at least one of fibers,filaments, bicomponent fibers, bicomponent filaments, biconstituentfibers and biconstituent filaments. The extruded web material issubstantially free of cellulose materials from natural sources. Theextruded web material can comprise one or more layers and can comprisepost-formation treatments.

Machine direction (MD)—The direction of travel of the forming surfaceonto which fibers are deposited during formation of a nonwoven web.

Meltblown fiber—A fiber formed by extruding a molten thermoplasticmaterial as filaments from a plurality of fine, usually circular, diecapillaries into a high velocity gas (e.g., air) stream which attenuatesthe filaments of molten thermoplastic material to reduce their diameter.Thereafter, the meltblown fibers are carried by the high velocity gasstream and are deposited on a collecting surface to form a web ofrandomly dispersed meltblown fibers. Meltblown fibers are generallydiscontinuous. The meltblown process includes the meltspray process.

Non-thermoplastic material—Any material which does not fall within thedefinition of thermoplastic material.

Nonwoven fabric or web—A web having a structure of individual fiberswhich are interlaid, but not in an identifiable manner as in a knittedfabric. Nonwoven fabrics or webs have been formed from many processessuch as for example, meltblowing processes, spunbonding processes, andwater laying processes. The basis weight of nonwoven fabrics is usuallyexpressed in grams per square meter (gsm) and the fiber fineness ismeasured in denier.

Polymer—Generally includes, for example, homopolymers, copolymers, suchas for example, block, graft, random and alternating copolymers,terpolymers, etc, and blends and modifications thereof. Furthermore,unless otherwise specifically limited, the term “polymer” includes allpossible geometrical configurations of the material. Theseconfigurations include, for example, isotactic, syndiotactic and randomsymmetries.

Spunbond fiber—A fiber formed by extruding molten thermoplasticmaterials as filaments from a plurality of fine, usually circular,capillaries of a spinneret. The diameter of the extruded filaments isthen rapidly reduced as by, for example, eductive drawing and/or otherwell-known spunbonding mechanisms. Spunbond fibers are generallycontinuous with deniers within the range of about 0.1 to 5 or more.

Thermoplastic—A polymer that is fusible, softening when exposed to heatand returning generally to its unsoftened state when cooled to roomtemperature. Thermoplastic materials include, for example, polyvinylchlorides, some polyesters, polyamides, polyfluorocarbons, polyolefins,some polyurethanes, polystyrenes, polyvinyl alcohol, caprolactams,copolymers of ethylene and at least one vinyl monomer (e.g., poly(ethylene vinyl acetates), cellulose esters and acrylic resins.

Two-phase spunbond material—A two-ply, fibrous, nonwoven web materialcomprised of a first layer or phase spun from a thermoplastic polymeroverlaid by a second layer or phase spun from a thermoplastic polymer.The first and second layers are joined or bonded to form the two-phasematerial.

SUMMARY OF THE INVENTION

Briefly stated, one aspect of the invention comprises a spunbonded ormeltblown extruded web material for use with conventional heat andpressure type sealing processes and equipment. The inventive webmaterial can be a two phase material comprised of a first layer orbarrier phase extruded from a thermoplastic polymer having a firstmelting point overlaid by a second layer or heat seal phase extrudedfrom a thermoplastic polymer having a second melting point. The meltingpoint of the heat seal phase is lower than the melting point of thebarrier phase. The first and second layers are joined to form thetwo-phase material. The two layers can be joined by well known methodssuch as, for example, extruding, calendering, air bonding, adhesivebonding, embossing, etc.

When surfaces of the two heat seal layers are placed in contact underheat and pressure, the thermoplastic fibers therein flow and fuse,bonding the heat seal layers together. The barrier layer has a highermelting point than the heat seal layer and functions as a barrier toprevent the lower melting point polymer of the heat seal layer fromsticking to the heated sealing equipment. The inventive web materialwill have a bleed through of 40 grams or less when tested as laterdescribed.

Many thermoplastic polymers or combinations of thermoplastic polymerscan be used for the heat seal phase, such as, for example,polypropylene, polyethylene, polyester and polyamide. The heat sealphase may comprise bicomponent or biconstituent fibers. Biodegradablethermoplastic polymers, for example, aliphatic or partly aromatic amidesand aliphatic or partly aromatic polyesters such as polylactic acid, canalso be used for the heat seal phase.

Many thermoplastic polymers or combinations of thermoplastic polymerscan be used for the barrier phase, such as, for example, polypropylene,polyethylene, polyester and polyamide. Biodegradable thermoplasticpolymers, for example, aliphatic or partly aromatic amides and aliphaticor partly aromatic polyesters such as polylactic acid, can also be usedfor the barrier phase. The barrier phase may comprise bicomponent orbiconstituent fibers.

For a two phase, extruded web material, the basis weight of each of thetwo phases can be in the range of about 0.5 gsm to about 40 gsm.Advantageously the basis weight of the heat seal phase is in the rangeof about 2 to about 12 gsm and the basis weight of the barrier phase isin the range of about 8 to about 18 gsm.

The basis weight of the extruded web material will be less than about 80gsm. For a preferred two layer material, the basis weight willadvantageously be within the range of about 10 to about 30 gsm, with anominal basis weight of about 16.5 gsm.

Fiber denier and fiber shape may be varied in known ways to best suitfinal end use requirements (for example, to achieve desiredsift/infusion properties for specific beverage precursor materials).Typically, fiber deniers will range from, for example, 0.1 to 5 denierand advantageously about 0.5 denier to about 3 denier.

The extruded web material can be provided with agents, for examplebinder, antistatic, surfactant, repellant materials and combinationsthereof to further improve nonwoven material characteristics. The agentor agents can be added during production of the extruded web material,for example by adding antistatic agents to the melt zone of theextruder. The agent or agents can also be added after production of theextruded web material, for example by using a size press to add binderto the web material.

Briefly stated, another aspect of the invention comprises a spunbondedor meltblown extruded web material having reduced elongation whencompared to conventional spunbonded or meltblown web materials.Advantageously the nonwoven materials of this aspect of the inventionhave a machine direction (MD) elongation under 1000 gm tension in therange of about 0.5 percent to about 3 percent. In some embodiments thenonwoven material of this aspect of the invention can be provided withpostformation treatments including, for example calendering, embossingand/or addition of a binder agent to provide the reduced elongation. Thereduced elongation is required for use on existing high speed packingmachinery.

Briefly stated, another aspect of the invention comprises a spunbondedor meltblown extruded web material having a minimum combination ofproperties making that material suitable for use as an infusionpackaging material. Preferably, the web material embodying this aspectof the invention is free from perforations or punctures, has a firstcolor time of less than about 13 seconds and a percent transmittance ofless than about 75%.

It is an object of the present invention to provide a new and improvedextruded web material.

Another embodiment described herein is a method of forming a multi-layerinfusion sheet material comprising extruding a thermoplastic spunbondedbarrier layer, extruding a thermoplastic spunbonded heat seal layer,joining the barrier layer to the heat seal layer by at least one ofcalendering and use of a binder, the calendering and/or binder impartingreduced elongation to the infusion sheet material such that the infusionsheet material has a dry elongation value in the range of 0.5 percent to3 percent under a 1000 gram load (TAPPI T494 OM 88 method).

It is another object of the invention to provide spunbonded extruded webmaterial that can be processed on conventional heat and pressure typesealing equipment.

It is a further object of the invention to provide a spunbonded extrudedweb material that retains the desirable porosity and infusioncharacteristics of conventional heat seal infusion web materials.

A better understanding of the invention will be obtained from thefollowing detailed description of the article and the desired features,properties, characteristics, and the relation of the elements as well asthe process steps, one with respect to each of the others, as set forthand exemplified in the description and illustrative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an inventive extruded web materialarranged for heat sealing in a “bleed through” test;

FIG. 2 is a schematic view of an inventive extruded web materialarranged for tensile testing in a “bleed through” test; and

FIG. 3 is a schematic illustration of a conventional packing machineusing a heat and pressure type seal process for formation of theinventive extruded web material into infusion packages.

DETAILED DESCRIPTION

One aspect of the invention includes an extruded web material comprisingthermoplastic fibers or filaments and suitable for use on conventionalheat and pressure type sealing equipment without causing excessive orobjectionable build up on the heated sealing surfaces thereof. Anotheraspect of the invention includes an extruded web material comprisingthermoplastic fibers or filaments and suitable for use on existing highspeed packing equipment. A further aspect of the invention includes anextruded web material comprising thermoplastic fibers or filaments andsubstantially retaining the desirable infusion properties characteristicof wet laid cellulose based infusion web materials.

In general, the nonwoven extruded web material of the invention can beprepared from noncontinuous fibers, continuous filaments, or acombination thereof. At present, the continuous filaments produced byspunbond techniques are preferred, although meltblown techniques thatproduce noncontinuous fibers are also considered to be within the scopeof this invention. The fibers and/or filaments useful in the inventiveextruded web material can include single polymer, bicomponent,biconstituent and mixtures thereof.

The spunbond process generally uses a hopper that supplies polymer to aheated extruder. The extruder supplies melted polymer to a spinneretwhere the polymer is fiberized as it passes through fine openingsarranged in one or more rows in the spinneret, forming a curtain offilaments. The filaments are usually quenched with air at a lowpressure, drawn, usually pneumatically and deposited on a moving belt or“forming wire” to form the nonwoven fabric. Polymers useful in thespunbonding process generally have a process melting point ortemperature of between about 80° C. to about 320° C. (176° F. to 610°F.). More preferably, the polymers will have a process melting point ortemperature of between about 110° C. to about 260° C. (230° F. to 500°F.).

Polymers such as, for example, polyethylene, polypropylene, polyethyleneterephthalate and polyamide can be used in the extruded web material.Biodegradable thermoplastic polymers, for example, aliphatic or partlyaromatic amides and aliphatic or partly aromatic polyesters such aspolylactic acid, can also be used for the barrier phase.

The fibers useful in practicing the invention are usually in the rangeof from about 0.1 to about 5 denier and more preferably about 0.5 toabout 3 denier depending on process conditions and the desired end usefor the fabrics to be produced from such fibers. The fiber denier may beadjusted in well-known fashion, such as by increasing the polymermolecular weight, decreasing the processing temperature or changing thequench fluid temperature and/or pneumatic draw pressure.

The fibers useful in practicing the invention can be bicomponent fibersarranged with a first polymer sheath surrounding a second polymer coreor in a side by side arrangement. Biconstituent fibers can also beuseful in the invention. Fiber shape can be varied to suit final end userequirements.

The extruded web material of the invention is advantageously comprisedof multiple phases or layers, incorporating a higher melting pointthermoplastic polymer in one layer and a lower melting pointthermoplastic polymer in a different layer. The layers are joined by anyof a number of well known techniques including, but not limited to,extruding one layer onto another layer, adhesive bonding, needlepunching, ultrasonic bonding, thermal embossing and thermal calendering.More than two layers may be used in practicing the invention. Such amultiple layer extruded web material can be an embodiment wherein someof the layers are comprised of spunbond filaments and some layers arecomprised of meltblown fibers, such as a spunbond/meltblown/spunbondlaminate or a spunbond/spunbond laminate. A spunbond/spunbond laminatemay be made by sequentially depositing onto a moving conveyor belt orforming wire a first spunbond fiber layer, then depositing anotherspunbond layer over the first spunbond layer and joining the layers.Naturally, both layers could be extruded in staggered fashion so thatmultiple layered web materials can be formed in a single pass.Alternatively, the layers can be made individually, collected in rolls,and combined in a separate joining step.

It should be kept in mind that in the above description the lower andhigher melting point layers could each be either the first laid down orthe second laid down webs. As a point of clarification, it should benoted that the term “first laid down web” refers to a web which has beenformed earlier in the processing line, or alternatively to a web whichhas been made and rolled up in a previous step. It should also be notedthat as used herein, and particularly in the claims, the terms “first”and “second” are arbitrary designations which do not necessarily referto their order of forming.

The extruded web material of the invention has a basis weight of about 1to 80 gsm. In multiple layer embodiments, each layer can have a basisweight of about 0.5 to about 40 gsm. For a preferred two layerembodiment, the heat seal phase can have a basis weight of 2 to 12 gsmand the barrier phase will have a basis weight of 8 to 18 gsm so thatthe basis weight for the finished two phase web material will be about10 to 30 gsm and nominally 16.5 gsm. Most preferably, the heat sealphase will have a basis weight of about 8 gsm and the barrier phase willhave a basis weight of about 8 gsm so that the basis weight for thefinished two phase web material will be about 16 gsm.

Naturally, a heat sealable extruded web material must be capable offorming a heat seal seam of sufficient strength for the intendedapplication. A “dry delamination strength test” measures the maximumforce required to separate a dry, heat-sealed seam within a webmaterial.

Dry Delamination Strength Test

The spunbonded web material is folded in half so that each face of thelower melting point phase is adjacent or touching and each highermelting point phase faces outward. Optionally, the folded web is placedwithin a folded piece of cellulose fiber paper of identical or largersize. The cellulose paper functions to prevent sticking of the lowermelting point heat seal phase to the heated surfaces of a heat sealmachine in web materials with higher bleed through. The spunbonded webmaterial within the cellulose paper is than placed under heat andpressure to form a heat seal seam as described below.

The heat seal seam is formed between the web material by pressing thefolded spunbonded web material/cellulose paper combination between theheated jaws of a thermal bar type heat sealing machine. The heat andpressure causes the thermoplastic fibers within the lower melting pointphases to flow and fuse to form a seam. The heat sealing machine shouldprovide a one inch wide seam. A SENTINEL 12-AS thermal bar heat sealeravailable from Sentinel Machinery of Hyannis Mass. has been foundsuitable. The jaw temperature is dependent on the materials beingjoined. Typically the jaw temperature should be at least 10° C. higherthan the melting point of the lowest melting point material for anadequate seam to be formed. Typically, the jaws are maintained atpneumatic cylinder pressure of 72 psi, imposing a force on the jaws thatis maintained for a dwell time of 0.38 seconds.

After imposing heat and pressure on the sample, the heat sealed webmaterial/cellulose paper combination is removed from the heat sealmachine and the spunbonded web material is separated from the cellulosepaper. The heat-sealed sample is cut to obtain a one-inch wide testsample with the heat sealed seam traversing the width of the sample.Each side of the heat sealed web material is clamped in a jaw of atensile test instrument. The seam is placed under an increasing tensileforce and the maximum force required to effect seam failure is recorded.The maximum force required to separate the heat-sealed seam representsthe dry delamination strength. Minimum acceptable dry delaminationstrength for a web material used for infusion applications will be 150gm and more preferably about 300 gm.

The strength of the heat seal seam in a hot, aqueous environment is alsoimportant in certain applications such as infusion packaging, where theseam is immersed in hot or boiling water. A “wet delamination strengthtest” measures the time required to separate a heat-sealed seam placedunder a specified load in a hot, aqueous environment.

Wet Delamination Strength Test

A six inch long by two inch wide test specimen of heat sealable webmaterial is folded to form a loop with the lower melting point heat sealphases touching at the edges. Heat and pressure is applied as above tocreate a 0.25 inch wide heat sealed seam joining the edges of the testspecimen loop. The joined loop is suspended in a distilled water bathheated to about 200° F. with the seam positioned midway between the topand bottom of the loop. A weight is placed within the bottom of the loopand the time required for the seam to break is recorded. Minimumacceptable heat seal seam wet delamination time for the inventiveextruded web materials using a 100 gm weight will be 600 seconds. Morepreferably the heat seal seam wet delamination time will be about 1200seconds.

In some embodiments of the invention, an important aspect of theinventive extruded web material is compatibility with conventional heatand pressure type sealing equipment. To ensure such compatibility, thespunbonded web material must not only provide an adequately strongheat-sealed seam, but also resist leaving deposits on the heated sealingsurfaces. It is undesirable for the lower melting point heat seal phaseof the spunbonded material to flow or “bleed through” the higher meltingpoint base phase during heat sealing operations such as in tea bagproduction. This bleed through behavior results in “build-up andcontamination of the heat seal equipment. To measure the resistance ofthe spunbonded web material to build up on heated surfaces a “bleedthrough test” is used.

Bleed Through Test

With reference to FIG. 1, the spunbonded web material 10 is folded inhalf so that the faces of each higher melting point phase 12 areadjacent and each lower melting point phase 14 faces outwardly. Thefolded web is placed within a folded piece of cellulose fiber paper 16of identical or larger size. The cellulose paper functions to preventsticking of the lower melting point heat seal phase to the heatedsurfaces of a heat seal machine. The spunbonded web material within thecellulose paper is than placed under heat and pressure (shown by arrows)to form a heat seal seam as more fully described below.

The heat seal seam is formed between the web material sides by pressingthe folded spunbonded web material/cellulose paper combination betweenthe heated jaws of a thermal bar type heat sealing machine. The heatsealing machine should provide a one inch wide seam. A SENTINEL 12-ASthermal bar heat sealer has been found suitable for use in this test.Typically, the jaws are maintained a pneumatic cylinder pressure of 72psi, imposing a force on the jaws, which is maintained for a dwell timeof 0.5 seconds. The jaw temperature is dependent on the materials beingjoined. Typically the jaw temperature should be at least 10° C. higherthan the melting point of the lowest melting point material for anadequate seam to be formed.

After imposing heat and pressure on the sample, the heat sealed webmaterial/cellulose paper combination is removed from the heat sealer andthe web material is separated from the cellulose paper. The heat-sealedsample is cut to obtain a one inch wide by one half-inch long testsample with the heat sealed seam traversing the width of the sample.Each side of the heat sealed web material is clamped in a jaw of atensile test instrument as shown in FIG. 2. The seam is placed under anincreasing tensile force and the maximum force required to effect seamfailure is recorded. The maximum force required to separate the heatsealed seam represents a measure of the level of “bleed through” of thelower melting point heat seal phase through the higher melting pointbase phase. A high maximum force value recorded in the bleed throughtest indicates that web material has a high probability of experiencingundesirable thermoplastic fiber build up and contamination conditionswith conventional heat and pressure type sealing equipment. Presently,it is preferred that a heat sealable spunbonded web material has a bleedthrough of 40 grams or less. It should be noted that if the heat sealmachine jaw temperature were sufficiently high, the barrier phase wouldalso be induced to melt, flow and seal.

To test a single-phase material for bleed through behavior, thesingle-phase spunbonded web material is folded in half to providecontacting sides and the folded web material is placed within a foldedpiece of cellulose fiber paper. The spunbonded web material within thecellulose paper is placed under heat and pressure to form a heat sealseam as previously described. The web material will also be bonded tothe cellulose paper. The heat sealed material is cut to obtain a oneinch wide test sample comprising a layer of cellulose paper joined to alayer of spunbonded web material by the heat sealed seam traversing thewidth of the sample. Each layer is clamped in the jaws of a tensile testinstrument, the seam is placed under an increasing tensile force and themaximum force required to separate the bond between the web material andcellulose fiber paper is recorded. The maximum force required representsa measure of the level of “bleed through” of the lower melting pointheat seal phase through the cellulose paper layer.

Conventional cellulose based heat and pressure sealable nonwoven webmaterial is often fed from a roll onto high speed web handling machinerysuch as equipment used to prepare single serving infusion packages oftea or coffee. As schematically represented in FIG. 3 the packing andsealing equipment 18 typically disposes a beverage precursor material 20between two portions of web material 22, 24. The heat seal phases 14 ofeach portion 22, 24 are adjacent with the barrier phases of each portion22, 24 facing outwardly. The portions 22, 24 with beverage precursormaterial 20 are fed through a heat and pressure type sealing unit 26 toform a heat seal seam in the portions 22, 24, enclosing the beverageprecursor material therein. The portions 22, 24 are separated to forminfusion packages 28. Some examples of such high speed packing machineryusing heat and pressure type sealing processes include the EC12single-lane packaging machine manufactured by Mai s.a. of Mar de Plata,Argentina (EC12) that can prepare 150 infusion packages per minute; theRotorex single-lane packaging machine manufactured by Delamere &Williams of Toronto, Canada (D & W) that can prepare 350 infusionpackages per minute; the type 1000 4-lane packaging machine manufacturedby Technipac Engineering of Ronford, Essex, U.K. (TECHNIPAC) that canprepare 800 infusion packages per minute and the C51 two-lane machinemanufactured by IMA Industrial Machine Automatiche S.p.A. of Bologna,Italy (C51) that can prepare approximately 2,000 infusion packages perminute. Such equipment is required to feed web material at speeds up to250 feet per minute in order to prepare infusion packages at the aboverates. Surprisingly, high speed web handling machinery such as the aboveinfusion package packing and sealing equipment has been found to operatebest within narrow ranges of product thickness, stiffness andelongation. In aspects of the invention for use with such equipment, itis advantageous that the inventive extruded web material has a thicknessin the range of about 30 to about 100 microns (μ) and preferably in therange of about 50 to about 80 (W.

Nonwoven web material dry elongation is measured by a “dry elongationtest”. The dry elongation test is performed in accordance with TAPPITest Method T494 OM 88. An Instron 1122 tensile test instrument can beadvantageously used in conjunction with the dry elongation test. For a1000 gram load it is advantageous that the inventive extruded webmaterial have a dry elongation in the range of about 0.5 percent toabout 3 percent. Preferably the dry elongation is in the range of about0.5 percent to about 2 percent.

In embodiments of the invention used for the preparation of infusionpackages containing tea, buildup and retention of a charge of staticelectricity on the web material can be a concern. The static charge canattract tea particles to seam areas or across the interior surface ofthe infusion package, causing a less desirable appearance of thefinished product. The ability of a web to discharge a static electricitybuildup can be measured by an “electrostatic decay test”.

Electrostatic Decay Test

A three inch by five and one half inch test specimen is cut from anonwoven web with the greater length as the direction to be tested. Thetest specimen is conditioned by placement in a controlled environmenthaving a relative humidity of 50±4% and a temperature of 73.4±2° F. forat least 10 minutes. The test specimen is placed between the electrodesof a static decay meter with the side to be measured facing the sensinghead. A Static Decay Meter model 406C from Electro-Tech Systems, Inc. ofGlenside, Pa. 19038 has been found suitable. The test specimen isinductively charged with 5,000 volts DC. The maximum voltage developedon the test specimen is measured and the time required for dissipationto ten percent of the measured maximum voltage is determined. It isbelieved to be advantageous that the inventive extruded web materialused for tea containing infusion packages have a static decay in therange of about 1 second to about 60 seconds and preferably in the rangeof about 1 second to about 40 seconds.

In some embodiments the inventive extruded web material can incorporateadditional processing steps such as calendering or embossing. Thecalendering or embossing processes partially melt and fuse some of thefibers in the material. These post-formation processes increase webstiffness, which can be beneficial in some applications.

In some embodiments the inventive extruded web material can incorporatean additional material such as, for example, at least one of bindermaterial, antistatic agent, surfactant or repellant to further improvespunbonded material characteristics. The material or materials can beadded during production of the extruded web material, for example byadding antistatic agents to the melt zone of the extruder. The materialor materials can also be added after production of the extruded webmaterial, for example by using a size press to add binder to the webmaterial. In one embodiment of the invention, the inventive extruded webmaterial is treated throughout its extent with a binder material which,when set or cured, is insoluble in aqueous solutions and unaffected byboiling water. The binder provides increased strength, stiffness andreduced elongation. Additionally, the binder material utilized accordingto the invention should exhibit an affinity for being readily absorbedinto the fibers of the web material. In embodiments of the inventionwherein the inventive extruded web material is used for infusionpackaging the binder material must provide the above desirableproperties while substantially retaining the porosity of the web andwithout adversely affecting the desirable infusion characteristics ofthe treated web material. Accordingly, the materials used herein aredistinguished from materials that form solid films over the treatedarea.

The binder materials found to be useful in the invention include, forexample, carboxylated polystyrene, SBR based materials, PVA basedmaterials and acrylic dispersion polymers. TN586 available from B. F.Goodrich of Cleveland, Ohio has been found suitable for use in theinvention. Naturally, other binder materials providing the desiredstrength, stiffness and/or reduced elongation properties to the extrudedweb material would also be useful in the invention and are encompassedtherein.

The binder material may be applied to the preformed extruded webmaterial by well-known techniques used to add such materials whileensuring complete coverage of the web material. For example, the webmaterial may be treated by brush, roller, spray, foam or immersion bathto effectuate the desired binder material application to the webmaterial. Since complete impregnation of the web material is desired, asaturation treatment is preferred. The binder emulsions generallypenetrate quickly through the rather thin and absorbent web material andmay be applied during a suitable stage in the manufacture of the fibrousweb material. For example, a saturating size press containing the bindermaterial may be used prior to the final drying and collection of the webmaterial. After treating the extruded web material with the dispersionof binder material, which very quickly permeates through the entirethickness of the web material, the treated web material is subjected toa thermal or heat cure in order to set the binder and prevent leachingof the binder material from the web material.

The binder material may be applied in undiluted form or may be dilutedwith water to provide the desired binder concentration, viscosity andpick up by the web material during application. The binder materialshould be applied so that the finished web material may have a binderloading, within the range of about 1 percent to about 50 percent of thefinal web material basis weight. Preferably the finished web materialhas a binder loading within the range of about 5 percent to about 30percent of the final web material basis weight. Calendering and/orembossing can be used in combination with the above additionalmaterials.

It should be realized that every nonwoven web material, whether wetlaid, spunbond or melt blown, is not suited for use in infusionpackaging. Acceptable infusion web materials must have suitable porosityto permit infusion yet also be free of perforations. Generally porosityis influenced by, e.g. basis weight of the web material. Infusion webmaterials must also have a minimum combination of seam strength, waterpermeability, and infusion properties. For ease of understanding andclarity of description, the invention is below described in itsapplication to heat sealable porous infusion web materials for use inthe manufacture of tea bags and the like.

Some infusion characteristics of importance relative to heat sealableextruded web material for infusion use relate to the rate at which watercan pass into the tea bag and tea liquor can pass out of the tea bag aswell as the degree of extraction which is able to take place within aspecified time. This is usually reported in terms of “first color” and“percent transmittance”, respectively.

First Color Time Test

When testing for first color, a tea bag made from the material to betested is carefully placed in quiet distilled water after the water hasbeen brought to a boil. Using a stopwatch, the time is recorded at whichthe first amber stream appears at the bottom of the sample. For a webmaterial having a basis weight of about 14 gsm, a first color time ofless than 12 seconds is required with less than 10 seconds beingpreferred. A first color of about 5-7 seconds is considered indicativeof excellent infusion characteristics. Of course, thicker, heavier basisweight materials typically will have higher first color values thanlighter basis weight materials.

Percent Transmittance

The percent transmittance test is conducted by measuring thetransmittance of the brew after a 60 second steep time using acolorimeter set at a wavelength of 530 mμ and a 1 cm optical path cell.A target value for good infusion is in the mid-sixty percentile rangewith transmittance decreasing as infusion improves.

Sift refers to the ability of a nonwoven web material to retainparticles of a specified size. Naturally, this property is important toinfusion packaging that must retain finely ground tea or coffeeparticles within the packaging. Sift is measured by a “sift test”.

Sift Test

The sand is placed in a jar and a sample of web material is secured overthe mouth of the jar. The surface area of the web material being testedis 8.6 square inches. A cup is placed over the web material to collectparticles sifting through the web material. The assembly is shaken oroscillated for fourteen minutes. Sift is usually measured as a percentloss of sand particles of specified size. A sift test result of lessthan 30 percent loss is desired for infusion web applications and aresult of less than 10 percent loss is preferred.

One aspect of the invention comprises an extruded web material for usein preparing infusion packages on high speed packing equipment usingheat and pressure type sealing processes. In this application theinventive extruded web material must provide a combination of stiffnessand minimal dry elongation to allow acceptable use with high speedpacking equipment; adequate seam strength to permit sealing of thebeverage precursor material within the infusion package using heat andpressure type processes; minimal bleed through to minimize buildup ofweb material on the heated sealing surfaces and acceptable infusionproperties to allow use of the finished infusion package to form a brew.

Having generally described the invention, the following examples areincluded for purposes of illustration so that the invention may be morereadily understood. The below described machine trials are based on useof the inventive extruded web materials on conventional packing machinesusing heat and pressure sealing processes and equipment under conditionstypically used with conventional, cellulose based, heat sealablenonwoven materials. While some of the inventive web materials may haveexhibited unacceptable properties under some conditions, it should beunderstood that use of the same extruded web material under slightlydifferent conditions or in different applications can be acceptable.Therefore the following examples are in no way intended to limit thescope of the invention unless otherwise specifically indicated.

Examples 1-4

A number of single layer web materials were prepared and tested forspecific infusion characteristics. Example 1 was a comparative webmaterial comprising a two-phase, wet laid, heat sealable, cellulosefiber based nonwoven web material typically used in infusionapplications. The non-heat seal or barrier phase comprises cellulosematerials and the heat seal phase comprises polypropylene fibers. Thematerial of Example 1 typically has a basis weight of about 16.5 gsm.

Example 2 comprised a single layer extruded web material of spunbondedpolyethylene terephthalate (PET) filaments. The material of Example 2had a basis weight of 15 gsm.

Example 3 comprised a single layer extruded web material of spunbondedbicomponent filaments. The bicomponent filaments of Example 3 comprisedpolyethylene and polyester polymers arranged in a sheath/coreconfiguration respectively. The material of Example 3 had a basis weightof 15 gsm.

Example 4 comprised a single layer extruded web material of spunbondedpolypropylene (PP) filaments. The web material of Example 4 was preparedon REIFENHAUSER spunbonding equipment available from Reifenhauser ofTroisdorf, Germany. The material of Example 4 had a basis weight of 15gsm. Each of the Examples was tested for first color and percenttransmittance. The results are summarized in Table 1 below.

TABLE 1 Comp. Example 1 Example 2 Example 3 Example 4 first color (sec.)5.7 6.13 6.04 4.78 transmittance (%) 69.9 64.7 70.5 70.8

Examples 2-4 exhibited excellent first color values for use in infusionpackaging. Examples 3 and 4 exhibited somewhat high, although acceptablepercent transmittance values for use in infusion packaging.

Examples 5-8

A number of single and multiple layer extruded web materials wereproduced. Example 5 comprised a single layer extruded web material ofspunbonded polypropylene having a melting temperature of about 162° C.ESCORENE PP3155 from Exxon Chemical, Polymers Group, of Houston, Tex. isan example of a polypropylene material having a melting temperature ofabout 162° C. such as used in Example 5.

Example 6 comprised a single layer extruded web material of spunbondedpolypropylene having a melting temperature of about 151° C. ACHIEVE 3825from Exxon Chemical, Polymers Group, of Houston, Tex. is an example of apolypropylene material having a melting temperature of about 151° C.such as used in Example 6.

Example 7 comprised a two-layer extruded web material. A layer ofspunbonded polypropylene having a melting temperature of about 162° C.(ESCORENE PP3155) was overlaid with a layer of spunbonded polypropylenehaving a melting temperature of about 151° C. (ACHIEVE 3825).

Example 8 comprised a two-layer extruded web material. A layer ofspunbonded polypropylene having a melting temperature of about 162° C.(ESCOREN E PP3155) was overlaid with a layer of spunbonded polyethylenehaving a melting temperature of 125° C. ASPUN 6811A from Dow Chemical ofMidland, Mich. is an example of a polyethylene material having a meltingpoint of about 125° C. such as used in Example 8.

Each of the inventive web materials in Examples 5-8 had a final webmaterial basis weight of about 16.5 gsm. This basis weight was afunction of equipment setup. Other basis weights can be used dependingon parameters such as particular equipment, polymers used and end userequirements. All of the fibers produced in Examples 5-8 were round incross-sectional shape.

Each of materials in Examples 5-8 was prepared on spunbonding equipment.The multi-layer web materials of Examples 7 and 8 were prepared byextruding a base layer. The formed base layer was run through thespunbonding equipment a second time and the second layer was extrudedonto the base layer. After extrusion of the second layer, the webmaterial was run through a thermal embosser to join the layers. Samplesof web materials from Examples 5-8 were hot calendered through a pair ofsteel rolls to increase stiffness. One of the rolls was heated to about250-260° F.

Each of the materials in Examples 5-8 was tested for seam drydelamination strength (both MD and CD directions), seam wet delaminationstrength (both MD and CD directions), bleed through and selectedinfusion characteristics. The results are summarized in Table 2.

TABLE 2 Example 5 Example 6 Example 7 Example 8 polymer PP PP PP/PPPP/PE melting point 162 151 162/151 162/125 (° C.) denier 0.85 0.850.85/0.85 0.85/1.7  bleed through 10 47 4 524 (gm) MD CD MD CD MD CD MDCD dry delamination  131  195  805  343  618  348  605  215 strength(gm/25 mm width) wet delamination 1200 1200 1200 1200 1200 1200 12001200 strength (gm/25 mm width) first color (sec) 8.89 6.28 5.57 7.95transmittance 72.0 69.0 71.0 68.5 (%) “A” sand sift 0.92 1.57 1.52 85.28(%)

The single ply extruded web material of Example 5 produced slightlylower than desired dry delamination strength values; good wetdelamination strength values and acceptable bleed through values. Theweb material of Example 5 exhibited good first color time; slightlyhigher than preferred percent transmittance values and very good siftvalues.

The single ply extruded web material of Example 6 produced very good drydelamination strength values; good wet delamination strength values, buthigher than preferred bleed through values. The web material of Example6 exhibited excellent first color time; slightly higher than preferredpercent transmittance values and very good sift values.

The two-phase extruded web material of Example 7 produced very good dryand wet delamination strength values and very low bleed through. The webmaterial of Example 7 exhibited excellent first color time; slightlyhigher than preferred percent transmittance values and very good siftvalues.

The two-phase extruded web material of Example 8 produced very good dryand wet delamination strength values, but unacceptably high bleedthrough values. The web material of Example 8 exhibited a good firstcolor time and good percent transmittance values. This web materialexhibited unacceptable sift values.

A roll of the extruded web material of Example 5 was run on an EC12machine. Typically, the EC12 machine is run at a heat seal stationtemperature of 120° C. with cellulose based nonwoven material such asexemplified by comparative Example 1. At 120° C. a buildup ofpolypropylene from the extruded web material was apparent on thesurfaces of the heat sealer unit. The heat seal station temperature wasreduced to a temperature of 85° C. where buildup on the heat sealer unitwas eliminated; however the packages produced had no heat seal seamstrength.

A roll of the extruded web material of Example 7 was run on an EC12machine. As the heat seal station temperature was raised from 85° C. to101° C., the heat seal seams began to “wrinkle”. The seam wrinklingindicated shrinkage of the lower melting point layer. In this heat sealstation temperature range the heat seal seams were judged by the packingmachine operator to have unacceptable seam strength as compared to heatseal seams formed in conventional cellulose based nonwoven material. Theextruded web material did not have sufficient stiffness for the stringof sealed packages to be cut into individual packages.

A roll of the extruded web material of Example 7 was run on a D & Wmachine. The D & W machine is typically run at a heat seal stationtemperature of 150° C. with conventional cellulose based nonwovenmaterial as exemplified by comparative Example 1. On this type ofmachine the web material is first cut into individual pieces beforebeing passed through the heat seal station for heat seal seam formation.In a heat seal station temperature range of 135° C. to 171° C. theinfusion packages produced were judged by the packing machine operatorto have unacceptable heat seal seam strength as compared to infusionpackages produced from cellulose based nonwoven material. Theunacceptable heat seal seam strength is believed to be an artifact ofstretching of the inventive web material under tension and subsequentrelaxation during the cutting operation, resulting in seam areas thatwere narrower than desired.

A roll of the extruded web material of Example 8 was run on the EC12machine. In the heat seal station temperature range of 80° C. to 92° C.the inventive web material had a tendency to melt on a tension controlroller adjacent to the heat seal station. In this heat seal temperaturerange the infusion packages produced were judged by the packing machineoperator to have unacceptable heat seal seam strength as compared toinfusion packages produced using cellulose based nonwoven material. Theinventive web material did not have sufficient stiffness for the stringof sealed infusion packages to be cut into individual packages.

In summary, the extruded web materials of Examples 7 and 8 hadinsufficient stiffness and dimensional stability during heat sealing foracceptable performance on the above packing machines using heat andpressure type sealing processes as compared to cellulose based nonwovenmaterial on the same machines and under the same conditions.

Examples 9-22

Example 9 was a single phase, extruded web material comprisingspunbonded polyethylene terephthalate filaments. Each filament had adenier of about 1. The polyethylene terephthalate filaments had amelting point of about 250° C. F61 HC available from Eastman Chemical ofKingsport Tenn. is an example of a polyethylene terephthalate materialhaving a melting point of about 250° C. as used in Example 9. The webmaterial of Example 9 had a basis weight of about 8 gsm.

Example 10 was a single phase extruded web material comprisingspunbonded bicomponent filaments. Each filament was in a sheath overcore configuration and had a denier of about 0.5. Each filamentcomprised a sheath of polypropylene having a melting point of about 162°C. (ESCORENE 3155) and a core of polyethylene terephthalate having amelting point of 250° C. (F61 HC). The ratio by weight of sheathmaterial to core material was about 1:1. The web material of Example 10had a basis weight of about 8 gsm.

Example 11 comprised a two phase extruded web material produced byextruding the material of Example 10 over the preformed web of Example9. The two phases exhibited some adhesion after extrusion of the secondphase over the first phase. The two phases were further joined bycalendering with a point-bonded calendering roll with a point surfacearea of twenty percent. The calender roll was heated to 150° C. Theextruded web material of Example 11 comprised a first phase of about 0.5denier bicomponent filaments having a polypropylene sheath (meltingpoint of about 162° C.) over a polyethylene terephthalate core (meltingpoint of about 250° C.) overlying a second phase of about 1 denierpolyethylene terephthalate filaments (melting point about 250° C.). Thebasis weight for the web material of Example 11 was about 16 gsm.

Example 12 was a single phase extruded web material comprisingspunbonded bicomponent filaments. Each filament was in a sheath overcore configuration and had a denier of about 0.9. Each filamentcomprised a sheath of polyethylene having a melting point of about 125°C. (ASPUN 6811) and a core of polyethylene terephthalate having amelting point of 250 C (F61 HC). The ratio by weight of sheath materialto core material was about 1:1. The web material of Example 12 had abasis weight of about 8 gsm.

Example 13 comprised a two phase extruded web material produced byextruding the material of Example 12 over the preformed web of Example9. The two phases exhibited some adhesion after extrusion of the secondphase over the first phase. The two phases were further joined bycalendering with a point-bonded calendering roll with a point surfacearea of twenty percent. The calender roll was heated to 110° C. The webmaterial of Example 13 comprised a first phase of about 0.9 denierbicomponent filaments having a polyethylene sheath (melting point ofabout 125° C.) over a polyethylene terephthalate core (melting point ofabout 250° C.) overlying a second phase of about 1 denier polyethyleneterephthalate filaments (melting point of about 250° C.). The basisweight for the web material of Example 13 was about 16 gsm.

Example 14 was a single phase extruded web material comprisingspunbonded bicomponent filaments. Each filament was in a side by sideconfiguration and had a denier of about 0.9. Each filament comprised aside of polyethylene having a melting point of about 125° C. (ASPUN6811) attached to a side of polyethylene terephthalate having a meltingpoint of 250° C. (F61 HC). The ratio by weight of one side to the otherside was about 1:1. The web material of Example 14 had a basis weight ofabout 8 gsm.

Example 15 comprised a two phase extruded web material produced byextruding the material of Example 14 over the preformed web of Example9. The two phases exhibited some adhesion after extrusion of the secondphase over the first phase. The two phases were further joined bycalendering with a point-bonded calendering roll with a point surfacearea of twenty percent. The calender roll was heated to 110° C. Theextruded web material of Example 15 comprised a first phase of about 0.9denier bicomponent filaments having a polyethylene side (melting pointof about 125° C.) attached to a polyethylene terephthalate side (meltingpoint of about 250° C.) overlying a second phase of about 1 denierpolyethylene terephthalate filaments (melting point of about 250° C.).The basis weight for the web material of Example 15 was about 16 gsm.

Example 16 was a single phase nonwoven spunbond extruded web materialcomprising bicomponent filaments. Each filament was in a side by sideconfiguration and had a denier of about 0.5. Each filament comprised aside of polypropylene having a melting point of about 162° C. (ESCORENE3155) and a side of polyethylene terephthalate having a melting point of250° C. (F61 HC). The ratio by weight of one side to the other side wasabout 1:1. The web material of Example 16 had a basis weight of about 8gsm.

Example 17 comprised a two phase extruded web material produced byextruding the material of Example 16 over the preformed web of Example9. The two phases exhibited some adhesion after extrusion of the secondphase over the first phase. The two phases were further joined bycalendering with a point-bonded calendering roll with a point surfacearea of twenty percent. The calender roll was heated to 150° C. The webmaterial of Example 17 comprised a first phase of about 0.5 denierbicomponent filaments having a polypropylene side (melting point ofabout 162° C.) attached to a polyethylene terephthalate side (meltingpoint of about 250° C.) overlying a second phase of about 1 denierpolyethylene terephthalate filaments (melting point of about 250° C.).The web material of Example 17 had a basis weight of about 16 gsm.

Example 18 was a single phase extruded web material comprisingspunbonded filaments of about 1.1 denier. Each filament was comprised ofpolypropylene having a melting point of about 162° C. (ESCOREN E 3155).The web material of Example 18 had a basis weight of about 8 gsm.

Example 19 was a single phase extruded web material comprisingspunbonded bicomponent filaments. Each filament was in a side by sideconfiguration and had a denier of about 1.7. Each filament comprised aside of polypropylene having a melting point of about 162° C. (ESCORENE3155) attached to a side of polyethylene having a melting point of about125° C. (ASPUN 6811). The ratio by weight of one side to the other sidewas about 1:1. The web material of Example 19 had a basis weight ofabout 8 gsm.

Example 20 comprised a two phase nonwoven extruded web material producedby extruding the material of Example 19 over the preformed web ofExample 18. The two phases exhibited some adhesion after extrusion ofthe second phase over the first phase. The two phases were furtherjoined by calendering with a point-bonded calendering roll with a pointsurface area of twenty percent. The calender roll was heated to 140° C.The web material of Example 20 comprised a first phase of about 1.7denier bicomponent filaments having a polypropylene side (melting pointabout 162° C.) attached to a polyethylene side (melting point about 125°C.) overlying a second phase of about 1.1 denier filaments comprised ofpolypropylene (melting point about 162° C.). The basis weight for theweb material of Example 20 was about 16 gsm.

Example 21 comprises a portion of the extruded web material produced asExample 11 and calendered after web formation using one smooth, steelroll and one smooth rubber roll. The steel roll was heated to about 150°C. and the rubber roll was left at ambient temperature. The polyethyleneterephthalate base phase faced toward the heated roll duringcalendering.

Example 22 comprises a portion of the extruded web material produced asExample 13 and calendered after web formation using one smooth, steelroll and one smooth rubber roll. The steel roll was heated to about 125°C. and the rubber roll was left at ambient temperature. The polyethyleneterephthalate base phase faced toward the heated roll duringcalendering.

The extruded web material of Example 20 was run on a D & W machine. Theheat seal station of the D & W machine was set at 140° C. The webmaterial of Example 20 generally maintained dimensional stabilitythroughout the D & W machine, although some web stretching under tensionwas noticed. The Example 20 web material exhibited good cuttability ofthe web material into pieces prior to the heat seal station. Infusionpackages produced had heat seal seams that were judged by the packingmachine operator to be unacceptable as compared to infusion packagesmade from conventional cellulose based nonwoven material. Dimensionalstability of the heat seal seam was judged by the packing machineoperator to be acceptable. It is believed that stretching of theinventive web material under tension resulted in some heat seal seams ofnarrow width. Increasing the heat seal station temperature to 151° C.increased heat seal seam strength to acceptable levels, howevershrinkage of the web in the heat seal station was noted.

The extruded web material of Example 21 was run on a C51 machine.Typically the C51 machine is used with cellulose based, heat sealable,nonwoven material such as exemplified by comparative Example 1. The heatseal station of the C51 machine was set at 180° C. The C51 machineincludes a slitting station before the heat seal station to slit webmaterial in the machine direction as the web material is travelingthrough the machine. The slitting station in this machine used anon-motorized blade. The web material of Example 21 did not havesufficient stiffness to be slit at the non-motorized slitting station ofthe C51 machine

The web material of Example 21 was run on a different C51 machine. Theslitting station (before the heat seal station) in this machine used amotorized blade. At a heat seal station temperature of 160° C., infusionpackages formed were judged by the packing machine operator to beacceptable for seam strength and seam dimensional stability (materialshrinkage during sealing) as compared to infusion packages made withcellulose based nonwoven material. No buildup of material at the heatseal station was noted. The web material cut well at the slittingstation, but the web material had insufficient stiffness for the stringof infusion packages to be cut into sets of two infusion packages.

The extruded web material of Example 22 was run on a C51 machine. Theslitting station in this machine (before the heat seal station) used amotorized blade. At heat seal station temperatures in the range of 130°C. to 160° C., infusion packages were judged by the packing machineoperator to be acceptable for seam strength and seam dimensionalstability (material shrinkage during sealing) compared to infusionpackages made from cellulose based nonwoven material. No buildup ofmaterial at the heat seal station was noted. The inventive web materialcut well at the slitting station. The string of infusion packages couldalso be cut into sets of two infusion packages, however the inventiveweb material had insufficient stiffness to be cut by a non-motorizedblade into individual infusion packages.

The extruded web material of Example 22 was run on an EC12 machine. Theheat seal station of the EC12 machine was set to at a temperature of 96°C. The web material of Example 22 maintained dimensional stability overthe EC12 tension rollers better than the web material of Example 8. Theheat seal seams of infusion packages made with the Example 22 materialwere judged by the packing machine operator to have acceptable strengthas compared to infusion packages made from conventional cellulose basednonwoven material. Dimensional stability of heat seal seams (materialshrinkage during sealing) was also judged by the packing machineoperator to be acceptable. The inventive web material had insufficientstiffness for cutting of the string of infusion packages into individualpackages.

The extruded web material of Example 22 was run on a D & W machine. Theheat seal station of the D & W machine was set at 149° C. The webmaterial of Example 22 generally maintained dimensional stabilitythroughout the D & W machine better than the web material of Example 7,although some web stretching under tension was noticed. The Example 22web material exhibited good cuttability of the web material into piecesbefore the heat seal station. Infusion packages produced on the D & Wmachine had heat seal seams that were judged by the packing machineoperator to be acceptable as compared to infusion packages made fromconventional cellulose based nonwoven material. Dimensional stability ofthe heat seal seam (material shrinkage during sealing) was also judgedby the packing machine operator to be acceptable. It is believed thatstretching of the inventive web material under tension resulted in someheat seal seams of narrow width.

The web materials of Examples 21 and 22 were run together on a TECHNIPACmachine. The TECHNIPAC machine seals together nonwoven material from twoseparate rolls running simultaneously to form an infusion package.Typically, the nonwoven material used is cellulose based. The heat sealstation of the TECHNIPAC machine was set at 165° C. The web materialseach exhibited good cuttability in both the machine and cross machinedirections and dimensional stability during heat sealing (materialshrinkage during sealing). Infusion packages produced at this sealingtemperature were judged by the packing machine operator to be acceptableas compared to infusion packages made from conventional cellulose basednonwoven material.

In summary, the extruded web materials of Examples 21 and 22 haddimensional stability during heat sealing (material shrinkage duringsealing) and heat seal seam strength that was comparable to conventionalcellulose based nonwoven material produced on the same machines underthe same conditions. On some machine types, the extruded web materialsof Examples 21 and 22 exhibited insufficient stiffness for some cuttingoperations as compared to conventional cellulose based nonwovenmaterial.

Examples 23-27

Example 23 comprises a portion of the extruded web material produced asExample 11 and treated with an acrylic binder mixture to increase webmaterial stiffness.

The binder mixture comprised:

100 parts water 22 parts binder 0.3 parts ammonium hydroxide 0.2 partssurfactant trace defoamerThe binder mixture was applied in a commercial size press to achieve acalculated binder pickup level of 20 percent after which the webmaterial was dried. No antistatic agent was used. The extruded webmaterials of Examples 21 (calendered) and 23 (binder treated) weretested for physical properties. The results of this testing are listedin Table 3.

Example 24 comprises a portion of the extruded web material produced asExample 13 and treated with an acrylic binder mixture to increase webmaterial stiffness. The binder mixture was the same as described withreference to Example 23. The binder mixture was applied in a commercialsize press to achieve a calculated binder pickup level of 20 percentafter which the web material was dried. No antistatic agent was used.The extruded web materials of Examples 22 (calendered) and 24 (bindertreated) were tested for physical properties. The results of thistesting are listed in Table 3. Also, included in Table 3 are selectedphysical properties for a conventional heat sealable cellulose fiberbased web material listed as Example 25.

TABLE 3 Example Example Example Example Example 25 21 23 22 24 basisweight (gsm) 16.5 16 19 16 19 dry elongation MD 0.2 0.9 0.7 1.1 0.8 250gm load (%) dry elongation MD 0.3 1.8 1.3 2.0 1.2 500 gm load (%) dryelongation MD 0.4 4.3 2.0 4.2 1.6 750 gm load (%) dry elongation MD 0.59.2 3.4 8.8 2.1 1000 gm load (%) sealing jaw temp (F) 376 340 340 290290 bleed through (gm) 1 1 1 5 21 22 dry delamination MD 190 410 540 810890 (gm/25 mm width) dry delamination CD 150 340 670 540 410 (gm/25 mmwidth) wet delamination MD >1200 >1200 >1200 >1200 >1200 (sec) [100 gm]wet delamination CD >1200 >1200 >1200 >1200 >1200 (sec) [100 gm] firstcolor (sec) 6.5 8.4 7.2 9.1 7.0 transmittance (%) 62.2 62.2 56 58.8 57.0“A” sand sift (%) 10 73 73 27 31 porosity (l/min/100 cc) 890 1640 21701620 1700 positive static delay 1.1 infinity 41 infinity 40 (sec)negative static delay 1.2 120 0.1 infinity 39 (sec)

As can be seen from the results of Table 3, the binder treatmentincreases extruded web material stiffness (as measured by MD dryelongation) and decreases static buildup. Surprisingly, the bindertreatment has little effect on the remaining properties of the inventiveweb material. As shown by the dry elongation results, the inventive webmaterials, both binder free and binder treated, are not as stiff asconventional, cellulose based, heat sealable web material (Example 25).

Example 26 comprises a portion of the extruded web material produced asExample 11 and calendered between steel rolls after web formation. Thepolyethylene terephthalate base phase was in contact with a smooth,heated steel roll and the polypropylene sheath over polyethyleneterephthalate core heat seal phase was in contact with a smooth,unheated steel roll. The top roll was heated to about 190° C. The bottomroll was unheated, although the roll temperature increased to about 120°C. during running of the web material. The web material of Example 26was run at an initial roll speed of about fifty feet per minute,increasing to seventy five feet per minute during the run. The webmaterial of Example 26 was run at a constant pressure of about 600pounds per lineal inch.

Example 27 comprises a portion of the extruded web material produced asExample 13 and calendered between steel rolls after web formation. Thepolyethylene terephthalate base phase was in contact with a smooth,heated steel roll and the polyethylene sheath over polyethyleneterephthalate core heat seal phase was in contact with a smooth,unheated steel roll. The top roll was heated to about 182° C. initially,increasing to about 186° C. during running of the web material. Thebottom roll was unheated, although the roll temperature increased toabout 115° C. during running of the web material. The web material ofExample 27 was run at an initial roll speed of about fifty feet perminute, increasing to seventy five feet per minute during the run. Theweb material of Example 27 was run at a constant pressure of about 600pounds per lineal inch.

The extruded web material of Example 24 was run on a D & W machine. Theheat seal station temperature was reduced from 220° C. (the setting forconventional cellulose based heat sealable web material) to 150° C. TheExample 24 material ran well over the test period of a few minutes. Theinfusion packages produced had heat seal seams that were judged by thepacking machine operator to be acceptable as compared to infusionpackages made from conventional cellulose based nonwoven material. Therewas no problem with cutting the web material into pieces before the heatseal station. No material buildup was noted at the heat seal station. Avery few infusion packages having unsealed seams were found. The problemis believed due to contraction of the web material after cutting or webslippage in the machine. Tension on the web material was reduced whichseemed to improve this issue somewhat. It should be noted that eveninfusion packages having seams of smaller than normal area exhibitedacceptable seam strength.

The extruded web material of Example 24 was run on an EC12 machine. Theheat seal station temperature was reduced from 120° C. to 90° C. forthis trial. While there was some initial difficulty threading theinventive web material through the machine, once threaded the webmaterial conveyed with relative ease. The string of infusion packageswas easily cut into individual packages. Infusion packages producedduring the trial were judged by the packing machine operator to haveacceptable heat seal seam strength as compared to infusion packages madefrom conventional cellulose based nonwoven material. There was somedifficulty in adjusting the timing of the cutter that separatesindividual infusion packages from the string of finished infusionpackages. It is believed that adjustment of the machine would resolvethis difficulty, however, due to time constraints machine adjustment wasnot attempted.

The extruded web material of Example 24 was run on a C51 machine. Thenon motorized blade at the slitting station (before the heat sealstation) could not slit the inventive web material in the machinedirection, resulting in stoppage of this trial.

The extruded web material of Example 24 was run on a second C51 machine.The slitting station (before the heat seal station) in this machine useda motorized blade. The heat seal station of this machine was set atabout 130° C., a temperature that is significantly lower than typicallyused with conventional heat sealable cellulose based web materials.During this trial, the inventive web material processed easily andtracked well within the machine. The string of infusion packages cuteasily into individual packages. Infusion packages produced during thetrial were judged by the packing machine operator to have acceptableheat seal seam strength as compared to infusion packages made fromconventional cellulose based nonwoven material. No heat seal seams werefound to be missing in infusion packages produced during the trial.Width of the heat seal seam for each of the four sides of a number ofthe infusion bags produced was measured and recorded. The measured seamwidths were found to be comparable to the seam widths of infusionpackages prepared on the same machine using conventional heat sealablecellulose based web material. At the conclusion of the trial no build upor sticking of the web material on the machine was noted.

The extruded web material of Example 24 was placed onto both unwindstations of a TECHNIPAC machine. The heat seal station was set at 124°C. In spite of the roll of web material being slightly too wide, theinventive web material processed easily and numerous infusion packageswere produced. No significant problems were observed during the testrun. Web material tracking, cutting of the string of infusion packagesinto individual packages, and heat sealing were judged to be acceptableby the packing machine operator during this trial. Infusion packagesproduced during this trial were judged by the packing machine operatorto have acceptable heat seal seam strength as compared to infusionpackages made from conventional cellulose based nonwoven material.

The extruded web material of Example 26 was run on a D & W machine. Theheat seal station temperature was reduced from 220° C. (the setting forconventional cellulose based heat sealable web material) to 170° C. TheExample 26 material ran well over the test period of a few minutes. Theinfusion packages produced had heat seal seams that were judged by thepacking machine operator to have acceptable heat seal seam strength ascompared to infusion packages made from conventional cellulose basednonwoven material. There was no problem with cutting of the web materialinto pieces before the heat seal station. No material buildup was notedin the heat seal portion of the machine at the conclusion of the testperiod.

The extruded web material of Example 26 was run on an EC12 machine. Theheat seal station temperature was set at about 102° C. for this trial.The inventive web material conveyed with relative ease. The string offinished infusion packages was easily cut into individual packages.Infusion packages produced during the trial were judged by the packingmachine operator to have acceptable heat seal seam strength as comparedto infusion packages made from conventional cellulose based nonwovenmaterial. There was some difficulty in adjusting timing of the cutterseparating individual infusion packages off of the string of finishedinfusion packages.

The extruded web material of Example 26 was run on a C51 machine. Theslitting station (before the heat seal station) in this machine used anon-motorized blade. As was previously observed, the non motorized bladecould not slit the inventive web material in the machine directionresulting in stoppage of this trial.

The extruded web material of Example 26 was run on another C51 machine.The slitting station in this machine (before the heat seal station) useda motorized blade. The heat seal station of this machine was set atabout 160° C. During this trial the inventive web material ran “loosely”in the machine, leading to tracking problems at various stations. Thetracking problems contributed to variation in package to package heatseal seam width and problems with timing of the cutter separating thestring of infusion packages into sets of two infusion packages. However,when cutter timing was correct the machine easily cut the string intosets. Surprisingly, the heat seal seam strength was judged by thepacking machine operator to be acceptable as compared to infusionpackages made from conventional cellulose based nonwoven material evenfor seams of less than optimum width. At the conclusion of the trial nobuild up or sticking of the web material on the machine was noted.

The extruded web material of Example 27 was run on a D & W machine. Theheat seal station temperature was reduced from 220° C. (the setting forconventional heat sealable cellulose based web material) to 150° C. TheExample 27 material ran well over the test period of a few minutes.Infusion packages produced were judged by the packing machine operatorto have acceptable heat seal seam strength as compared to infusionpackages made from conventional cellulose based nonwoven material. Therewas no problem with cutting of the web material into pieces before theheat seal station. No material buildup was noted in the heat sealportion of the machine at the conclusion of the test period. A very fewinfusion packages having unsealed seams were found. The problem isbelieved due to contraction of the web material after cutting or webslippage in the machine. Tension on the web material was reduced whichseemed to improve this issue somewhat. Surprisingly, even infusionpackages having seams of smaller than normal area produced exhibitedadequate seam strengths.

The extruded web material of Example 27 was run on a C51 machine. Theslitting station (before the heat seal station) in this machine used amotorized blade. The heat seal station of this machine was set at about130° C., a temperature that is significantly lower than typically usedwith cellulose based heat sealable web materials. During this trial theinventive web material ran “loosely” in the machine, leading to trackingproblems at various stations. The tracking problems contributed tovariation in package to package heat seal seam width and problems withtiming of the cutter separating the string of infusion packages intosets of two infusion packages. However, when cutter timing was correctthe machine easily cut the string into sets. Surprisingly, the heat sealseam strength was judged by the packing machine operator to beacceptable as compared to infusion packages made from conventionalcellulose based nonwoven material even for seams of less than optimumwidth. At the conclusion of the trial no build up or sticking of the webmaterial on the machine was noted.

The materials of Examples 21-22 and 24-27 were tested for certainphysical properties and the results are listed in Table 4.

TABLE 4 Comp. Example Example Example Example Example Example 25 24 2726 21 22 basis weight 16.5 19 16 16 16 16 (gsm) thickness (mil) 92 80 5063 73 53 dry elongation 0.2 .8 0.4 0.5 0.9 1.1 MD 250 gm load (%) dryelongation 0.3 1.2 0.8 0.8 1.8 2.0 MD 500 gm load (%) dry elongation 0.41.6 1.2 1.2 4.3 4.2 MD 750 gm load (%) dry elongation 0.5 2.1 1.6 1.69.2 8.8 MD 1000 gm load (%) sealing jaw 376 290 290 340 340 290 temp (F)bleed through 11 22 4 1 1 21 (gm) dry 190 890 890 530 410 810delamination MD (gm/25 mm width) dry 150 410 460 460 340 540delamination CD (gm/25 mm width) wet >1200 >1200 >1200 >1200 >1200 >1200delamination MD (sec) [100 gm] wet >1200 >1200 >1200 >1200 >1200 >1200delamination CD (sec) [100 gm] first color (sec) 6.5 7.0 8.4 7.3 8.4 9.1Transmittance 62.2 57.0 58.6 58.7 62.2 58.8 (%) “A” sand sift 10 31 2764 73 27 (%) porosity 890 1700 1230 1870 1640 1620 (l/min/100 cc)positive static 1.1 40 infinity infinity infinity infinity decay (sec)negative static 1.2 39 240 infinity 120 infinity delay (sec)

As previously stated, comparative Example 25 is a conventional cellulosebased, wet laid, heat sealable web material exemplary of the webmaterials typically run on packing machines using heat and pressure typesealing processes. The strength and dry elongation under load propertiesof Examples 24, 26 and 27 are somewhat less desirable than the sameproperties of Example 25, although the web materials of Examples 26 and27 were successfully run on a variety of packing machines using heat andpressure type sealing processes. The web materials of Examples 24, 26and 27 also had infusion properties acceptable for use as infusionpackaging.

The web materials of Examples 21 and 22 are inferior in strength and dryelongation under load properties to the same properties of Examples 24,25, 26 and 27. The web materials of Examples 21 and 22 did not run aswell on the same variety of packing and sealing machines as the webmaterials of Examples of 24, 26 and 27.

As will be apparent to persons skilled in the art, variousmodifications, adaptations and variations of the foregoing specificdisclosure can be made without departing from the teaching of thepresent invention.

1. A method of forming a multi-layer infusion sheet material comprising:extruding a thermoplastic spunbonded barrier layer, extruding athermoplastic spunbonded heat seal layer, joining the barrier layer tothe heat seal layer by at least one of calendering and use of a binder,the calendering and/or binder imparting reduced elongation to theinfusion sheet material such that the infusion sheet material has a dryelongation value in the range of 0.5 percent to 3 percent under a 1000gram load when measured using the TAPPI T494 OM 88 test method.
 2. Themethod of claim 1, wherein the barrier layer is joined to the heat seallayer by calendering without inclusion of binder.
 3. The method of claim1, wherein the barrier layer is joined to the heat seal layer usingbinder without calendering.
 4. The method of claim 1, wherein thebarrier layer is joined to the heat seal layer using both calenderingand binder.
 5. The method of claim 1, wherein the barrier layer isjoined to the heat seal layer using thermal calendering.
 6. The methodof claim 1, wherein binder is used and comprises an acrylic material. 7.The method of claim 1, wherein binder is used and is absorbed into thespunbonded filaments while retaining the porosity of the sheet material.8. The method of claim 1, wherein the binder is applied to achieve acalculated binder pickup level of about 20%.
 9. The method of claim 1,wherein binder is applied by brush, roller, spray, foam or immersionbath.
 10. The method of claim 1, wherein binder is added using a sizepress.
 11. The method of claim 1, wherein the barrier layer comprisesbicomponent fibers.
 12. The method of claim 1, wherein binder is usedand comprises at least one member selected from the group consisting ofcarboxylated polystyrene, styrene butadiene rubber based materials,polyvinyl alcohol based materials and acrylic dispersion polymers. 13.The method of claim 1, wherein the barrier layer is biodegradable. 14.The method of claim 1, wherein the barrier layer comprises polylacticacid.
 15. The method of claim 1, wherein the binder comprises astiffening agent.
 16. The method of claim 1, wherein the infusion sheetmaterial has a basis weight in the range of about 1 to about 80 gramsper square meter.